Grease the locking lugs well.
I seem to shoot my best groups when ever the bolt needs to be forced closed. I know the bullet must fit snug without being pushed back too far into case, but consistent resistant bolt closing is important. As the throat erodes bolt closing will get easier. So seat the bullet longer to compensate and chamber pressures will have less spread or be more equal.
BTW I was really surprised to learn how quickly throat will erode. Especially when shooting lots of rounds and getting barrel hot.
I once read that antimony is very abrasive...? Or is the cleaning rod more abrasive?